The present invention relates to a method and apparatus for controlling the operation of electromagnetic control units, especially solenoid valves, used in internal combustion engines.
Conventionally, a high current is passed through the solenoid valve for rapid response for a rapid opening of the valve, and, after the valve opens, this current is then reduced to the so-called holding current. Thus, to open a solenoid valve rapidly, a higher current and thus a large energy storage means is required to make the rapid response energy available. This, in turn, entails a relatively high cost.
This invention is especially useful for opening and closing solenoid valves of carburetor units of internal combustion engines for blocking the carburetor units from idling fuel during a motor vehicle coasting operation.
Idling shutoff valves in carburetor units and the control of these valves are known. In such units, fuel feed via the idling nozzle of the carburetor is cut off when the ignition is turned off to prevent the internal combustion engine from continuing its running; a condition known as "dieseling".
On the other hand, certain known types of carburetors instead of cutting off the idling fuel feed, block the idling mixture by a blocking valve when the ignition is turned off. Such a mixture blocking valve has a relatively large mass so that increased current is required to open the valve in a vehicle coasting operation against the vacuum suction force, which force is high during this stage. This means that a correspondingly large armature and winding for the electromagnetic part of the valve is required.